Line and other popular messaging apps are apparently being blocked in China to censor a pro-democracy rally.

For the past several days, Japanese and overseas media outlets have been reporting that Line, the South Korean messaging app Kakao Talk and Yahoo Inc.’s photo-sharing service Flickr have been impaired.

The reports say that the Chinese government seems to be blocking the services to prevent coverage of a major pro-democracy rally that drew over a half million people to Hong Kong on Tuesday.

Tokyo-based Line Corp. said Friday that it was uncertain whether the problem had been solved as of Friday afternoon and that the cause was unknown. Line is a subsidiary of Internet services company Naver Corp. of South Korea.

Line Corp. did not disclose how many users it has in China but said it was the first time it had experienced this kind of problem in the communist country.

China has blocked such major SNS services as Facebook and Twitter in the past.